Air control for circulating systems and the like



Feb. 11, 1941. E. w. BALLENTINE AIR CONTROL FOR CIRCULATIHG SYSTEMS ARDTHE LIKE 3 Sheets-Sheet 1 Inverifor'; Earle WZB erfllne, wwa- Filed Feb.14, 1939 Feb. 11, 1941. E. w. BALLENTINE AIR CONTROL FOR CIRCULATINGSYSTEMS AND THE LIKE Filed Feb. 14, 1939 3 Shee ts-Sheet 2 InvHTor':

Henl'in Earle WIB gmmQ Feb. 11, 1941. E. w. BALLENTINE AIR CONTROL FORCIRCULATING SYSTEMS AND THE LIKE 3 Sheets-Sheet 3 Filed Feb. 14, 1939Invem'or': Ear eNMa'B enrin Patented Feb. 11, 1941 UNITED STATES-PATENTOFFICE AIR CONTROL FOR CIRCULATING SYSTEMS AND THE LIKE Earle W.Ballentine, Wilmette, Ili., assignor, by

mcsne assignments, to Russell Electric Corporation, a corporation ofIllinois Application February 14, 1939, Serial No. 256,397 3 Claims.(Cl. 230-274) The present invention relates to an improved especialreference to the conditions existing in cooling systems in which primaryreliance is placed on the circulation of the air in a room or otherenclosure, but is not limited to such use. In order that the features ofthe invention may be better understood I shall mention certain of thefactors governing cooling systems in relation to the cooling effectsproduced and governed by such factors.

The cooling effect may be effected eitherby reducing the relativehumidity of the air, or by reducing the absolute temperature of the air,or by circulating the air in the room or other enclosure wherein thecooling effect is desired; and by the term cooling effect I mean theeffective temperature which is felt by the observer or 0c.- cupant ofsuch room. The amount of power necessary to produce a given coolingeiIect in a given space and for a given number of occupants of suchspace is a maximum when such cooling effect is produced solely byreduction of relative humidity by mechanical means; is less when suchcooling effect is producer solely by actual lowering of absolutetemperature; and is a minimum when such cooling effect is producedsolely by air motion in the space in question; and of course the desiredcooling effect may be produced by a combination of two or more of suchmeans, with corresponding effect on total power consumption.Nevertheless the air motion system is the most economical of the severalschemes above defined, and greatly to be desired. This is especiallytrue of relatively large enclosures, such as auditoriums,

meeting places, large oflice rooms, and similar places. The rate of airmotion therein must, however, not be excessive, especially in the zoneof occupancy or levels where people are accommodated. Generallyspeaking, there is a reduction of the effective temperature" amountingto about 1.20 degrees F. for each hundred feet per minute of air flow insuch zone.

In large enclosures it is of course desired to obtain the desired rateof air flow uniformly over theentire zone of occupancy, so that nooccupied portion of such zone will be subjected to excessive rate offlow,-and also to ensure sufficient flow at all portions of such zone toproduce the desired cooling efiect therein.

In order to produce the desired air flow in such large enclosures it isalso desirable to make use of relatively large fan units, both in orderto reduce first cost thereof, and also on account of the higher totalefllciency thereby obtainable. Prior to the present invention it 'hasbeen impossible to provide such large fan units of design suitable forplacement directly in the enclosures to be cooled, since it has not beenpossible heretofore to secure with such units the desired uniformity offlow over the entire zone to be cooled; and neither has it been possibleto produce the desired carrying effect with such fans to cause the airto carry to the far portions of the enclosure, so that such far portionsespecially have been starved of the cooling effect, and a very unevencooling effect has been produced over such large enclosures. As a resultit has heretofore been necessary to make use of an excessive number ofsuch fan units, placed at various locations within the enclosure, withattendant high cost of installation, relatively smaller size of eachsuch fan unit, and corresponding lowered efficiency of operation.Furthermore, when using several such fan units placed at variouslocations within the enclosure, such units will frequently produce aircurrents flowing at cross flows, so that the distribution and coolingefiect are thereby greatly impaired.

In the type of circulating system herein referred to it is customary todirect the air flow from the fan located near one end or the enclosurealong an upper zone of the enclosure and above the zone of occupancy,towards the opposite end of the enclosure, so that the air draft thusflowed towards such opposite end will strike such opposite end of theenclosure and flow downwardly to the zone of occupancy; theme the aircurrent will flow backwardly along the zone of occupancy to the fan,producing the cooling efof the air stream has been due to the tendencyof the stream of air from the fan to become difiused or distributed overa rapidly increasing cross-sectional area (measured at right angles tothe direction of air flow from the fan), so that the air stream hasrapidly enlarged as it moved away from the fan, with correspondingreduction of rate of flow and loss of carrying power, as well asuncertainty as to distribution of the circulation at various portions ofthe enclosure.

It is to be noted that if the outwardly flowing stream from the fanreaches the opposite wall of the enclosure its flow will thereby bepositively arrested, and the stream will be caused to flow in the onlydirection it can go, namely, down to the zone of occupancy, and due tocontact with such far end wall there will be at that location adiffusion or distribution of the so-downwardly turned stream of air, sothat during the return movement it will flow at relatively slow speedand over the entire cross-sectional area of the zone of occupancy. Bythis meansit is possible to direct the outwardly flowing stream at ahigher rate than is desirable for the stream in the zone of occupancy,such outwardly flowing stream occupying a relatively smallcross-sectional area clear to the far end wall; and at the same time thereturning stream in the zone of occupancy will flow at the desired ratein such occupied zone, and over the entire cross-section of suchoccupied zone.

The main object of my present invention is to greatly increase thecarrying power of the stream of air coming off the fan unit, byreduction of the diffusion action of the air in such stream, therebyensuring delivery of a stream which will flow for a great distance fromthe fan unit with little increase of its cross-sectional area, so thatthe effective carrying power of such stream will be greatly increased,and the great benefits of such improvement may be realized in suchsystems as above discussed, as well as in other uses of the fan units.

I have discovered that the diffusion action in the air stream coming offthe fan is due almost entirely to the rotary component of motiondelivered to the air coming off the fan blades. In this connection it isnoted that the motion of the air moving off the blades includes both theforward component and also a rotary component; and such rotary componentdepends in large measure on the angle or pitch of the blades, but is acomponent which cannot be entirely avoided in conventional forms offans. Such rotary component of air motion in the stream tends to cause aspiraling movement of 'the air flowing away from the fan, and thisspiral or rotary movement necessarily produces a centrifugal action inthe air particles of the stream, so that as the air particles move awayfrom the fan unit they not only move forward, but also are thrownoutwardly from the true axis of the stream, and a diifusion orenlargement of the stream occurs. This enlarging action is progressiveon an increasing rate as the air flows away from the fan unit; and thecarrying power of the air stream rapidly falls due to the lowered rateof air movement along the axis of the stream, as well as to the factthat the enlargement of the stream is accompanied by a picking up ofadditional air (not coming from the fan unit), the momentum of whichadditional air must be produced by the air particles of the true stream,with a consequent great reduction of stream velocity, and a very rapidloss of stream carrying power.

I have found that by. removing the rotary component of movement oftheair immediately after the air leaves the fan blades, so that the airstream flows directly away from the fan unit substantially withoutrotary component of motion I am enabled to increase the carrying powerof the air stream to several times its previous carrying power, so thatI am enabled to throw the air stream from the fan several times as faras has formerly been possible, substantially without enlargement ordiffusion of such stream, thus making it possible to satisfactorilycirculate the air body within an enclosure correspondingly larger thanhas formerly been possible. Furthermore, it will be noted that when theoutgoing air stream becomes seriously diffused or enlarged beforereaching the far end wall, portions of such stream reach down into thepath of the returning current in the zone of occupancy, withcorresponding interference with the return current in the zone ofoccupancy; which effect is also obviated by the practice of the presentinvention.

Now the rotary component created in a particle of air coming off the fanblade depends largely on the angle or pitch of the blade at the locationof such air particle; and it is customary to design the blades with amaximum pitch or angle close .to the hub. Air particles coming off ofportions of the blade at successively greater radii measured from thehub have successively smaller rotary components of motion. I havetherefore provided means for removing the rotary components of motionfrom all particles of the air coming from all radial positions measuredalong the blades, in such manner that all particles of the air stream arequally and completely relieved of the rotary components of motion, andthe entire air stream, throughout its entire diameter is substantiallyfreed of any such rotary component of motion.

In connection with the foregoing it may be noted that a. radial fin,placed with its surface parallel to the axis of the air stream, andextending radially outwardly from the axis of the fan, will present asurface normal to the rotary component of motion, and that a series ofsuch fins extending radially outwards from the axis of the air streamwill present a series of air passages between them, said air passageshaving side surfaces normal to the axis of the stream, and the sizes ofsaid passages will increase, measured outwardly from the axis of thestream towards its outer limit. It is here noted that in order tocompletely remove the rotary component of motion the distance ordimensions of such fins measured in the direction of the stream axisshould be greater, in comparison to the distance between the fins, atpoints where the radial component is greater, than at points where suchradial component is lesserthat is, the ratio of fin length, parallel tothe axis, compared to distance between fins, across the air stream,should be a maximum close to the hub, and may then reduce as one movesaway from the axis of the stream and towards its outer limit. It is nownoted that by using fins of uniform dimension measured in the directionof the axis, and placed radially from the axis, and at uniform spacingaround the circle, and with their surfaces parallel to the direction ofthe air stream, I have provided an air controller of ideal design andarrangement, and one which will remove the rotary component of motionfrom all portions of the body of the air stream equally; and it is notedthat the dimensions of such fins parallel to the direction of air flowmay be quite small and still accomplish the result of complete removalof the rotary component of motion at all locations across the diameterof stream. I have found that an angular pitch of the blades close to thehub, amounting to substantially thirty-six (36) degrees, (measured fromthe plane normal to the axis), and tapering regularly to an angularpitch of substantially eight (8) degrees, at the tips of the blades willgive a maximum efiiciency of air movement over the entire radialdimension of the blades,

and in fact efficiencies as high as eighteen percent (18%) of the totalenergy input may be attained with such designs. These angular pitchesare much lower than have heretofore been generally accepted as the bestfor fan designs, but I have determined the correctness of this designfor maximum efficiency by a great number of experiments and with manyblade designs.

In connection with the foregoing, it is also noted that the rotarycomponent of motion of the air flowing away from the fan blades dependslargely on the angular pitch of the blades, and of course lowering ofsaid pitch therefore results in lowering of such rotary component ofmotion. It is therefore to be observed that such low angular pitchblades lend themselves admirably to use in connection with the means forensuring projection of an air stream substantially free of any rotarycomponent of motion, all as hereinbefore set forth, and therefore adouble benefit is secured by using such low angular pitch blades in thepresent connection. I

I'have discovered that the noise generated by the action of the air onthe blades may be greatly lessened or even eliminated by curving theblades into an arcuate form measured about a center ,displaced angularlyfrom the position of each the entire length of the blade, and acorresponding lessening of air noise is the result. Gener ally I preferto curve the blades so that the tips lead in the direction of rotation.

Furthermore, I prefer to so form the blades that the delivery edge ofeach bladelies within a plane normal to the axis of rotation, theleading edge of such blade lying within a warped plane. In thisconnection it is noted that a convenient manufacturing operation formaking these fans consists in casting them, and afterwards buffing orpolishing them. During these operations the blades frequently becomebent out of line or form, so that they must be bent or formed back intoproper curvature as intended.

By designing the blades so that one edge of each n blade, generally thedelivery edge, lies in a plane, it is possible to set .the fan down on aflat surface after it has been buffed or polished, and if it is out ofform such fact will appear from the existence of parts of such edgewhich do not lie in contact with such surface. It is then a very easymatter to bend the bladeback into form which result is evidenced by thecontacting of the entire edge with such flat surface.

Other objects and uses of the invention will appear from a detaileddescription of the same, whichconsists in the features of constructionand combinations of, parts hereinafter described and claimed.

In the drawings:

Figure 1 shows diagrammatically a large room or enclosure having thereina number of desks located in the cooling zone of occupancy, the figureshowing a vertical longitudinal section through such room, and thecirculating fan being mounted on a post at one end of the room to throwthe outflowing air stream to the far end of the room above the zone ofoccupancy, the,

air stream then striking the far wall and moving down to the zone ofoccupancy and returningin said zone to the beginning end of the room forrecirculation;

Figure 2 shows a plan view corresponding to Figure 1, looking down ontothe portion of the room treated by such fan;

Figure 3 shows a vertical elevation of a typical fan unit embodying thefeatures of the present invention, including the air director forremoving the rotary component of motion;

35 Figure 4 shows a face view of the air director for removing the-rotary component of motion from the air stream;

Figure 5 shows a cross-section on the line 55 of Figure 4, looking inthe direction of the arrows;

Figure 6 shows a plan or face view of a typical fan blade embodying thefeatures of the present invention, being a two'blade unit;

Figure 7 shows an edge view corresponding to Figure 6;

Figure 8 shows a fragmentary face view of the hub portion of the unit ofFigure 6, looking at the other face\ thereof as compared to Figure 6;and

Figures 9, 10, 11, 12, and 13 show cross-sections through one of theblades taken on the lines 99, Ill-'40, ll-ll, l2-I2 and I3 of Figure 6,looking in the directions of the arrows;

Referring first to Figures 1 and 2, the enclosure therein shown includesthe floor 20, ceiling 2!, near end wall 22 and far end wall 23. The sidewalls may be assumed to be at 24 (for the far side) and cut away (forthe near side). A number of desks or other work units are shown at 25,and these are of course 'all in the lower or zone of occupancy of theroom, namely, below the dotted line' 26 which extends horizontally alongthe room somewhat above the normal elevation of the occupants of theroom. The fan circulating unit is shown close to the wall 22, and

is designated by the numeral 21. It includes the stand 28 which holdsthe fan above the zone of occupancy and in line with the delivery zone,the fan unit proper 29 being carried by said stand and in line with thedelivery zone. This fan unit proper includes a fan 30 and motor 3|,together with the air director 32; and the details of the fan and airdirector are shown in Figures 4 to 13, inclusive, and will be describedhereinafter.

Referring again to Figures 1 and 2, the current of air delivered by thefan flows horizontally along the upper portion of the room and above thezone of occupancy as shown by the air stream 33, and it will be notedthat this stream continues substantially without diffusion clear fromthe fan unit to the opposite end wall 23, so that the delivered aircurrent flows somewhat in the form of a tubular body of air clear to thefar end wall. There is shown in Figures 1 and 2 a slight widening ofthis stream of air after it leaves the fan unit, but this is due to theviscosity of the air and not to any rotary component of motion; and dueto the removal of the rotary component by the means hereinafter enlargedupon I have secured a very great increase of the carrying power of theair stream, so that a full and definite stream of controlled air may bedelivered to great distances, as much as one hundred fifty or twohundred feet, substantially without diffusion.

At the far end this delivered air stream strikes the wall 23 and isimmediately diverted thereby, so that it becomes widened (until itstrikes side walls or other like streams of air from other units), andthen this stream flows toward-s the only location where it may beaccommodated, namely, downwardly to the lower portion of the room, andto a location beneath the outwardly flowing stream; and then theso-lowered stream flows backwardly along the zone of occupancy towardsthe point of beginning, and then upwardly back to the fan unit. It isthen again recirculated, following this circuit time after time. Now itis noted that the original-outwardly flowing stream is of comparativelysmall cross-sectional size, and does not occupy more than a portion ofthe width of the room (normal to the drawings of Figures 1 and 2),whereas the returning stream in the zone of occupancy fills the entirewidth of the room or the space to adjacent similar streams circulated byother similar fan units, so that the velocity of the returning air inthe zone of occupancy may be much less than the outgoing stream. Or, toput the matter another way, the outgoing stream may be delivered at amuch higher velocity than can be comfortably borne by the human body,thereby ensuring a great carrying power .to reach a distant end wall,and then the returning stream in the zone of occupancy may still flow ata velocity which is as great as may be properly used in such zone. Thusthe advantages of high velocity and great carrying power in the deliverystream are combined with the provision of a proper and comfortablevelocity in the zone of occupancy.

Referring now to Figure 3 the fan unit includes the motor 3| driving thefan 30, which is generally mounted directly on the motor shaft. A guard34 of wire or the like is placed around the fan proper; but the frontface of said guard is either modified or eliminated to form and providefor an air director 32. This air director is shown in detail in Figures4 and 5. It includes a series of radially placed plates or slats 35,located at uniform angular positions and extending outwardly radiallyfrom the axis of the fan, which is also the axis of the air stream.These plates lie in planes parallel to the axis of .the air stream andthe axis of the fan, and are of such width (or distance along thedirection of air flow) as to provide the desired corrective action. Itwill be noted that these plates, therefore stand in position to'receivethe rotary component of air movement norm-ally against flow of the airstream through the air director,

so that a full delivery velocity will still be ensured, and no loss'ofstream velocity will be occasioned.

Now it is noted that a single such directive plate would not properlyperform its function, so a suitable number of such platesis provided;and thereby there are established the angular shaped openings 36 betweensaid plates. Each of these openings increases in width from the axistowards the periphery of the director. (Generally a ring 31 is placed atthe center of the director, and in front of the fan hub since there islittle air delivery coming directly therefrom, and the inner ends of theplates 35 are connected thereto and supported thereby) The outer ends ofthe plate 35 are suitably connected to and supported by the guard, as bya ring 38.

Examination of Figure 5 shows that the plates 35 are of uniform width(distance along the axis of stream flow) throughout their radialdimension. The rotary component of the air movement is greatest close tothe axis of the air stream, where the blades have the maximum pitch, andis least at the tips of the blades. The axial length (width) of theplates 35 should be in direct ratio to the rotary component of movementto be removed from the air stream at any given point, measured radiallyfrom the axis of the stream, so that, as far as this factor alone isconcerned the plates 35 should taper in axial dimension (width) from amaximum at their inner ends, to a minimum at their outer ends, at thering 38. On the other hand, the axial dimension of said plates shouldbe, at each radial position measured from the stream axis, in proportionto the amount of 'air volume flowing at such position; and since theplates 35 spread apart from the center towards the outer periphery, sothat the air volumes of successive radial increments increaseproportionately, it follows that the plates 35 should be of uniformaxial dimension (width) as shown in Figure 5. Therefore, the use ofplates 35 of uniform axial dimension provides-an air director whichresponds to all requirements, as far as fully removing the rotarycomponent of the air movement is concerned. Furthermore, such platesrequire no special forming or cutting, but can be made from strip ofuniform width.

The edges of the plates 35 should be rounded or streamlined so as tointerfere the least amount with .the air flow through the director.Also, said plates should be as thin as is consistent with properrigidity and strength.

The diameter of the air director should approximate that of the fan, andthe director should be placed as close as possible to the fan,consistent with proper clearances. Thereby there will be assurance thatall portions of the air stream will be properly treated by the director,and that such treatment will be accorded before the centrifugal actionof the rotary component of air movement has had time to eifect anyappreciable dispersing action on the air stream.

. is not at the extreme tip.)

Thereby the full body of the air stream will leave the fan unitsubstantially without any motion except straight ahead, so that amaximum carrying effect will be available. .Tests over extended periodsof time, and under severe oper ating conditions have definitelyestablished the fact that the carrying effect and power of the airstream from relatively large fans (meaning such fans intended forcirculation in rooms and, other similar enclosures as for example 22inches in diameter) can be more than doubled by such an air director,with all the attendant advantages.

The details of the fan itself are shown in Figures Bto 13inclusive.Therein is shown a two blade fan, having the blades 39 and ll! carriedby the hub 41. These blades are, of course identical and placed atuniform angular separations. Each blade is formed with a twist of itspropelling surface (seen in Figure 6), commencing with a pitch ofsubstantially 36 degrees close to the hub (see Figure 9), and taperingto a twist of substantially 8 degrees at the tip. (Figures 9, 10, ll, 12and 13 are sections at successive radial positions along the blade, andthe section i3-l3 It will be noted that the pitches at the successivesections increase uniformly measured backwardly from the tip towards thehub, as is evident from comparison of Figures 9, 10, 11, 12 and 13 witheach other.

Examination of Figures 9 to 13 inclusive also shows that the propellantsurf-ace of the blade (tops of Figures 6, 9, 10, 11, 1-2 and 13) is soformed that all the sections show said top surface as being a straightline. In other words, this surface is generated by the movement of astraight line outwardly from the hub to the tip, and at the same timealtering the angle of tilt of such line (measured from the plane normalto the axis of rotation), with a uniform rate of change of such angle,so that, in effect, the propellant surface of the blade is a true warpedsurface.

It is also noted that each of the sections 8 to It inclusive is taken ona plane at right angles to the entering edge 40 of the blade, (thedirection of rotation is shown by the arrow), so the warping of saidsurface takes place with a movement of the generating line radiallyaround the center of curvature of the entering edge of the blade, andwith a movement of the pivoting point of said generating line along aline drawn through the center of curvature ll of the ensons which havealready been explained herein.

It is noted that by this formation of the blade there is also produced ablade having its width increasing from the hub to a position about halfway to the maximum radial dimension, and then again reducing in width tothe tip. Thereby there is produced a blade having its propellant surfaceat all radial locations substantially in proportion to the amount of airto be moved at such location (taking into account the propellant speedof the blade at such point). Generally the extreme tip of the bladeshould be curved as shown in Figure 6; and generally, also the curva-'ture of the entering edge 40 should be concave towards the direction ofblade movement, but

1 not necessarily so.

this type of fan; but I have already mentioned that I have found from alarge number of comprehensive tests and studies that the angles hereinshown give a maximum eiflciency of air movement, meaning thereby acomparison of the kinetic energy of the entire volume of the air streamwith the energy input to the fan itself. In fact, for fans ofsubstantially 22 inches diameter I have been able to secure efficienciesas high as eighteen percent of the total input, delivered as kineticenergy of the stream. This is far above the efllciencies which it hasheretofore been possible to secure in such devices.

Moreover, it is noted that the low pitch angles herein disclosed producea much lowered totary component of air movement as the air at any givensection leaves the blade, so that the work to be performed by the airdirector is correspondingly reduced, and the size of such air directormay be correspondingly reduced. Therefore the combination of such a fanblade with the air director herein disclosed is ideal for production ofan air stream which is substahtially'free of any rotary component ofmotion, and therefore best adapted for great carrying power; andtherefore best adapted for the circulation of air in large enclosures,and according to the system of cooling by air circulation as herein setout.

It may be noted that the guard 34 placed around the fan may be ofconventional design, comprising a series of wire rings of successivelydiflering diameters, connected together by a series of more or lessradial wire ties, as well shown in Figures 3, 4 and 5; and as thereshown, said guard may be carried around the back side of the fan, theair director being located at the front of said guard; or, as shown,within an opening in the front of said guard. In such case the ring 38of the air director may be suitably secured to the front of the guard,or to the edge of an opening in the front of the guard, as shown inFigures 4 and 5.

Furthermore, the fan unit is conveniently carried by a stand 28 oftelescoping tubular form. having the set screw M whereby the elevationof the fan proper may be adjusted to ensure delivery of the outgoing airstream at the proper elevation in the room. Also, suitable means (notshown in detail) may be provided for making it possible to adjust theangle of tilt of the fan so that the outgoing air stream will travel inthe proper direction.

- It may be'noted that the removal of the rotary component of motionfrom the air stream is in some respects similar to single polarizationof light, in the sense that the air motion in one component has beenremoved. I therefore sometimes speak of my air director herein disclosedas an air polarizer, it being understood that this term is purelyarbitrary, and in no sense a limitation of the invention as such.

It is noted that the cooling effect should be adjusted from time to timeby variation of fan speed with consequent variation of rate of aircirculation and flow. If the outgoing air stream were to contain arotary component of motion wide limits of variation and still maintaininall cases a stream flow in the outgoing stream 10 of substantiallylinear form and substantially free of diffusion or dispersion. Anysuitable speed adjustment may be used, such as a rheostat orautotransformer 45.

It is to be noted that a stream of air of linear form and free of rotarycomponent, such as herein contemplated, will flow linearly through theenclosing envelope of stationary air, somewhat after .the manner offlowage of such stream along a tube; and it is also to be noted that airhas viscosity. Therefore, the linearly flowing stream, free of rotarycomponent will have exerted on its marginal portion a drag, due tocontact with the enclosing envelope. This drag, and also the naturalviscosity of the flowing air stream, will cause a gradual widening ofthe outflowing stream, as shown by the arrangement of the full timearrows in Figure 2; but such widening is very much less than would havebeen caused by a -,rotary component of motion, and is due to anadflentirely different physical action than that due to rotary componentof motion, and is to be very clearly distinguished therefrom. The twoactions are not to be confused in aerodynamics.

wardly from the hub commencing with a pitch of substantially thirty-sixdegrees with respect to a plane normal to the axis of fan rotation,close to the fan hub, and ending with a pitch of substantially eightdegreeswith respect to said plane at the tips of the blades, to therebyobtain high efficiency of-sthe fan combined with low rotary motion ofthe delivered air, together with means WhileI have here-in shown anddescribed only to remove rotary component of motion from the airdelivered by said fan, comprising an air director placed close to thefan at the delivery side thereof and including a series of plateslocated in a plane normal to the axis of the air stream, 5 said plateshaving their surfaces parallel to the air stream, and said platesextending outwardly radially with respect to the axis of the air stream,whereby any rotary component of motion of air delivered by said fan isremoved from the air 10 stream immediately after leaving the fan blades,by contact of the spiralling air with the surfaces of the air director,substantially as described.

2. Means to generate an air stream by means of a blade fan and substatially free of rotary l5 component of motion comprising a fan unitincluding a blade fan and an air director in close proximity to thedelivery side of said fan, said blade fan having blades of relativelylow pitch angle on their propellant surfaces with consequent generationof a relatively small amount of rotary component of motion in thedelivered air stream, and the air director being located in closeproximity to said delivery side of the fan and including a series ofplates located in the air stream and having surfaces normal .to therotary component of air motion, said surfaces being parallel to the axisof the air stream, and each such surface of the air director having adimension parallel to the axis of the air stream at every pointproportional to the product of the fan blade pitch at such pointmultiplied by the distance between plates at such point, substantially"asdescribed.

3. Means to generate an air stream by means of a blade fan andsubstantially free of rotary component of motion comprising a fan unitincluding a blade fan and an air director in close proximity to thedelivery side of said fan, said blade fan having blades of relativelylow pitch angle on their propellant surfaces with consequent generationof a relatively small amount of rotary component of motion in thedelivered air stream, and the air director including a series of plateshaving their surfaces at right angles to the rotary component of motionand at all points substantially in surface area proportional to theamount of rotary component of the air in proximity to each pointmultiplied by the air space between plates at such point, substantiallyas 50 described.

EARLE W. BALLEN'I'INE.

